High voltage electric switch gear



Apml 1,8, i933. CHRSTIE ET AL 1,903,956

HIGH VOLTAGE ELECTRIC SWITCH GEAR Filed March 14, 1932 3 Sheets-Sheet lApril 18, 1933.

J. CHRISTIE ET AL HIGH VOLTAGE ELECTRIC SWITCH GEAR Filed March 14, 19323 Sheets-Sheet 2 JJM April 18, 1933.

J. CHRISTIE ET AL HIGH VOLTAGE ELECTRIC SWITCH GEAR Filed March 14, 19323 Sheets-Sheet 3 Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE JOHNCHRISTIE, OF SUNDERLAND, AND DONALD FOSTER AMER, OF JARROW, ENGLAND,ASSIGNORS TO A. REYROLLE & COMPANY LIMITED, OF HEBBURN-ON-TYNE, ENGLAND,A REGISTERED COMPANY F GREAT BRITAIN HIGH VOLTAGE ELECTRIC SWITCH GEARApplication led March 14, 1932, Serial No. 598,836, and in Great BritainApril 17, 1931.

This invention relates to high voltage electric switch gear and hasparticular reference to the mounting of potential transformer fuses insuch gear. As is well known such fuses are employed to protect theprimary circuits of the potential transformer, and it is customary tomount the fuses in separate oil filled tanks rinto which the connectionsfrom the potential transformer are led through plug and socket isolatingcontacts. In some instances isolation has also been effected bywithdrawing the fuse from its mounting.

The present invention has for its object to provide an improved mountingfor a potential transformer fuse which renders unnecessary the provisionof a special tank for the fuse and thereby enables considerable econonlyto be effected both in space and in cost.

A convenient practical arrangement of fuse mounting according to theinvention, as applied to A. C. switchgear wherein a singlephasepotential transformer is provided in each phase in association with anoil-immersed circuit-breaker for connecting a feeder circuit to abusbar, is illustrated by way of example in the accompanying drawings,in which Figure l shows a general View of a portion of the switch gearpartly in section to show the mechanism between the circuitbreaker andthe potential transformer,

Figure 2 shows the potential transformer fuse and its mounting invertical section on a larger scale,

Figures 3 and 4 also on a larger scale show respectively in sideelevation and in plan part of the mechanism at the top of the fusemounting, and

Figure 5 is a view similar to part of Figure 1 illustrating a modifiedformv of fuse mounting according to the invention. y

In the arrangement of Figures 1-4 two oilfilled chambers are providedabove the circuit-breaker tank A, into which the busbar and the feeder Bare respectively introduced. The busbar chamber is not shown in thedrawings since it forms no part of the present invention, but may bearranged for example in the manner described. in the present applicantsprior U. S. patent applica'- tion Serial No. 508,988, wherein the busbaris connected to one of the main circuit-breaker contacts through anisolating switch in the busbar chamber and through an insulatedconductor normally projecting into the circuit-breaker tank butwithdrawably mounted in an insulating tube passing through the busbarchamber. The other main circuitbreaker contact is similarly connectedthrough a withdrawable conductor to a contact on an insulating tube C1passing through the feeder chamber C. This contact is connected to ametal lug C2 to which an isolating switch blade Dis pivoted. Thisisolating switch blade D cooperates with a contact member B1 connectedto the feeder B and also with an earthed Contact D1.

The feeder chamber C extends over the potential transformer tank E,which is disposed by the side of the circuit-breaker tank A, and has anorifice in its bottom wall vertically above a corresponding orifice inthe cover plate E1 of the potential transformer tank E. The two orificesare connected by a short trunk E2, within which is mounted a condensertype bushing insulator F of usual construction, the length of thebushing being approximately the same as that of the potentialtransformer fuse G itself. The outermost layer of the bushing F isconnected to earth through the metal wall of the trunk E2, and theinnermostlayer is formed by a metal tube H whose lower end projects ashort distance beyond the bushing and carries a metal cap H1 to whichthe primary winding of the potential transformer is connected.

Closely fitting within the tube H and extending from the metal vcap H1right up to an orifice J in the top of the feeder chamber C is aninsulating tube K formed of layers of impregnated paper. This tube K islined in its lower part with further layers K1 of paper insulationextending approximately to the same height as the surrounding metal tubeH, and in its upper part with a second metal tube K2 resting on top ofsuch paper insulation K1 and extending nearly to the top oftheinsulating tube K. Metal conducting layers K1 are interleaved with thepaper lay- 100 CII ers of the insulatingtube in the neighbourhood of theupper end of the outer metal tube H and the lower end of the secondmetal tube K2.

The potential transformer fuse G itself is of the high resistancedust-lilled type and is inserted withinfthese tubes so that in itsoperative position its lower metal base rests on the metal cap H1 and isthus electrically connected tothepotential transformer primary windingandto-tliemetal 'tube'Il-I forming thev innermost layer of the bushingF, whilst its upper terminal is provided with spring contacts G1 orspring pressed plungers engaging with the vsecond metal tube K2. Thefuseis carriedl on an insulating handle G2 extend'- ing to the topoftheA insulating tube K, so

vthat the fuse can beireadily withdrawn by .the handle from itsmounting. The upper endv of the. insulating tube K is normally closedbya metal cap J1 which may press on the upper end of thehandle G2 and thushold .the fuse securely in' place. Y The space within the tube Ksurrounding the fuse G is preferably oil-filled'. c i Y f Theysecondmetal tube K2 near its upper endis connected through the wall oftheinsulating tube K to a metal lug K4 to which is'pivoted. anvisolating'switch blade L. This blade L cooperates with the Contactmember B1 connected tothey feeder B and also with an earthed contact L1mounted in a suitable po- 'sition in the feeder chamber C. Thisarrangement enables the second metal tube K2 and thereforeV also thefuse G to be earthed so'that the fuse can be withdrawn, when desired,with absolute safety. In order that the operator may readilyv see thatthe isolating switch .L isv in rits earthed position before withdrawingtheV fuse, an indicator maybe providedV outside the wall of the feederrcham` ber. This: indicator may conveniently bel actuated by a flexiblebellowsin the wall of the chamber, Vthis bellows being operated bymovement oftheisolating switch blade Lfi'nto the-earthed position'.SuchV an indicating arrangement is incorporated in the modified form offuse mounting shown in Figure 5 and will be described later withreference toY that figure'f i f If desired,the metal cap J1 closing thetop ofthe insulating tube K may be mechanicallyY interlocked withytheoperating mechanism for the isolating switch L, whereby removal ofthe .capv is prevented unless the isolating switch is in its earthedposition. Thusin one convenient arrangement the metal Ycap J1 is mountedat one side on a pivot pin J2 which is kcarried in suitable bearings AMon thetop of thefeeder chamber C so that it Y ,canl rotate therein'andycan also slide longi-A tudinally for a short distance.

In vthe normalpositionwith the cap J1 closed, a projection J 3 on theside ofthe pivot pin J2 abuts closely" against a" stop M1 4on the top ofthe i? chamberso that yit is impossible torotate the pin J2 to open thecap J1 without first sliding the pin longitudinally until the projectionJ 2 is clear of the stop M1. The operating mechanism for the isolatingswitch L is provided with a segmental plate Nrwhich, when the isolatingswitch` is closedlies beyond the end of the pivot pin J2 and preventslongitudinal movement thereof. Movement ofthe isolating switch into itsearthedlA position causes the segmental plate N' to move out of the pathof the pivot pin. Thus the metal cap J1 cannot be opened, when theisolating switch L is closed, but when the switch is earthed the capcanbe openedl by sliding and then rotating the'pivot pin J2. The cap vJ1 ispreferably bolted in its normal position, the bolts having first to beremoved before the cap can be opened. It will be noted that when the capis open, thek pivot pin J2 lies in the path of the segmental plate N andthus prevents movement of the isolating switch L into the closedposition.

Thus the fuse G when in its operative po,- sitfon constitutespart of theconnection from the potential transformer primary winding through theisolating switchL to theV feeder B and is directlyr mounted within, thete-rminal bushing F of the potential transformer. The use of a condensertype bushing prevents corona discharge from thethin wire of the fuse andthe insulating tube K serves to prevent the two ends of the fuse frombeing virtually short-circuited, as they would otherwise be, bytheinnermost layer of the condenser bushing. The condenser layers K3 act tograde-the stress set up when the fuse blows betweenA the lower end'ofthe metal tube K2 and the upper vend of the metal tube H which is at thepotential of the lower end o f the fuse. l

An alternativeV form vof mounting for the fuse is -illu-stratedin Figure5, which shows only those rparts of the arrangement which differ fromthe arrangement of Figures 1 4. In this modification the fuse G is asbefore mounted within an insulating tube K which extends through thefeeder chamber C coaXially with the condenser bushing F inthe trunk E2connecting the feeder chamber with the potential transformer tank E, butin this instance the condenser bushing F is of the usual constructionwith a central rod-like conductor terminating at its upper end in ametal cap Fl on which the lower end of the fuse G rests, the insulatingtubeK at its lower end surrounding thefupper part of the condenserbushing F instead of being mounted within it.V The upper end of theinsulating tube K is arranged in the same manner as in the arrangementof Figures l-4.

l/Vhen the fuse G is of the liquid-filled type. a limiting resistance Ois mounted lon top of` the fuse with its lower end attached to the cupper terminal of the fuse, so that the limiting resistance is in serieswith the fuse. f The resistance O and the fuse G thus togetherconstitute a unit which can be withdrawnas a whole through the upper endof the tube K by means of the insulating handle G2 as in the arrangementof Figures 1-4. The limiting resistance O may be omitted when the fuseis of the high resistance dust-filled type.

The upper end of the limiting resistance O (or of the fuse G as the casemay be) is provided with spring contacts or spring- Apressed plungers O1engaging with a conducting member K5 connected through the lwall of theinsulating tube K to a metal lug through the wall of the chamber C andcarrying a plate P1 pressed by a spring PL towards the chamber wall, anoil-tight joint being ensured by the provision of a flexible Vbellows P3connecting the plate P1 to the chamber wall. is connected to a lever Qwhich serves to actuate an indicator of suitable construction wherebythe operator can readily see whether or not the fuse is earthed beforewithdrawing the fuse. In the example illustrated the lever Q, carries aplate Q1 bearing suitable legends such as On and Off which areselectively eXposed to View through a window Q2 in accordance with theposition of the 40 `isolating switch blade L.

arrangement, metal conducting layers of short length are interleavedwith the paper layers to grade the stress set up when the fuse blowsbetween` conducting members connected to the upper and lower ends of thefuse. In this instance the conducting layers KG surround the fuse Gitself, the innermost layer being disposed around the lower end of thefuse and the outermost layer around the upper end of the fuse, whilstthe intervening layers overlap one another in a steplike formation.These layers thus grade the stress between the conducting member Kconnected to the isolating switch contact andthe metal cap F1 on thecentralconductor within the condenser bushing F, and therebyeliminate'or minimize risk of a flash-over betweeny these conductingmembers.V Although the potential transformer primary winding may beearthed in kthe usual manner so that the metal cap Fl at the lower endof the fuse is at earth potential, it may sometimes be preferable tooperate the transformer'withl out cai-thing one of its windings.V

The outer end of the rod P1 for high voltage electric switchgear, compIt will be-seen that either of the above arrangements provides aconvenient and compact mounting for the fuse, without the necessity fora separate containing tank, and is adequately safeguarded againstdisruptive discharges.

The arrangements described have been given by way of example only andmay be modified in variousways within the scope of the invention. Thusfor instance the fuse in the arrangement of Figures 1-4 may be of theliquid-filled type, in which case a limit- -ing resistance would bemounted inseries with and on` top of the fuse in the manner describedwith reference to Figure 5.

` What we claim as our invention and desire to secure by Letters Patentis 1 l. A potential transformer fuse mounting for high voltage electricswitchgear, comprising a potential `transformer tank, a condenser-typebushing insulator which supports thefuse mounting in the wall ofthetank, a metal tube constituting the innermost layer of the bushinginsulator, a potential transformer fuse disposed within the bushinginsulator, and an insulatingtube surrounding the fuse and surrounded bythe metal tube. v

2. A potential transformer fuse mounting prising a potential transformertank, a condenser-type bushing insulator which supports the fusemounting in the wall of the tank, a metal tube constituting theinnermost layer of the bushing insulator, a potential transformer fusedisposed within the bushing insulator, an insulating tube-surroundingthe fuse and surrounded by the metal tube, and an electrical connectionbetween the lower end'of the fuse within Vthe transformer tank and themetal tube.

3. A potential transformer fuse mounting for high voltage electricswitchgear, comprising a potential transformer tank, a condenser-typebushing insulator which supports the fuse mounting in the wall of thetank, a. metal tube constituting the innermost layer of the bushinginsulator, a potential transformer fuse disposed within the bushinginsulator, an insulating tube surrounding the fuse and surrounded by themetal tube, and means whereby the fuse can be withdrawn through theupper end of the insulating tube for isolating purposes.

4. A potential transformer fuse mounting for high voltage electricswitchgear, comprising a potential transformer tank, a condenser-typebushing insulator which supports the fuse mounting in the wall of thetank, a metal tube constituting theinnermost layer of the bushinginsulator, a potential transformer fuse disposed within the bushinginsulator, an insulating vtube surrounding the fusev and surrounded byLthe metal tube, a second metal tube mounted within the insulating tubeand electrically connected at its lower end to the upper end of thefuse, and an externalelectric circuit to which the second metal tube isconnected.

5;v A potential transformer fuse mounting for high voltage electricswitchgear, comprising a potential transformer tank, a condenser-typebushing insulator which sup- V ports the fuse mounting in the wall ofthe tank, a metal tube constituting the innermost layer of the bushinginsulator, a potential transformerfuse disposed within the .bushinginsulator, an insulating tube sur-V rounding the` fuse and surrounded bythe metal tube, a second metal tube mounted within the insulating tubeand electrically connected at its lower end to the upper end ofthe fuse,a Contact formed on the second metal tube constituting a terminal forcon- --nection to an external electric circuit, and an electricalconnection between the lower end of the fuse within the transformer tanklmost layer of the bushing insulator, a potential transformer fusedisposed within the bushingV insulator, an insulating tube surroundingthe fuse and surrounded by the `metal tube, such insulating tube beingformed of layers of insulating material, an electrical connectionbetween the lower end of thefuse within the transformer tank and themetal tube, and Vconducting layers interleaved with the insulatinglayers of the insulating tube 'between the upper ends of the n fuse andof the metal tube.V -f

f 7.y A potential transformer fuse mounting for high .voltage electricswitchgear, coniprising a potential transformer tank a condenser-typebushing insulator' which supports the fuse mounting in the wall ofthetank, a .metal tube constituting the innermost layer of the bushinginsulator, a 'p0- tential 'transformer fuse disposed within the .bushinginsulator, 'an insulating tube surrounding the fuse fand surrounded bythe metal tube, such insulating tube being formed of layers vofinsulating material, a second metal tube mounted within theinsulatingtube with its lower' end inV electrical connection with theupper end of the fuse, an external electric'circuit to which the secondmetal tube'islconnected, an electrical connection between the lower endof the fuse within the transformer tank and the first metal'tube, andoverlapping conducting layersof short length interleaved with the insu#lating layers of the insulating tube between the lower end of the secondmetal tube and the upper end of the first metalrtube.

8. A potential transformer fuse mounting for high voltage electricswitchgear, comprising a potential transformerV tank, ,a condenser-type.bushing insulator in the wall thereof, a conductor within the bushingin'- slator connected to the potential transformer primary winding, -aninsulating tube formed of layers of insulating material and disposedcoaXially withthe bushing insulator, a potential transformer fusemounted within such insulating tube', and overlapping conducting layersfof short length interleaved with the insulating layers of such tube andacting to grade the stress set up whenrthe fuse has blown betweenconducting members connected to the two ends of the fuse.

'r 9. A potential transformer fuse mounting for'high voltage electricswitchgear, comprising a potential transformer fuse, aninsulating tubeformed of Ylayers of insulating material'surrounding the potentialtransformer fuse, overlapping conducting layers of short lengthinterleaved with the insulating :layers of such tube and acting to gradethestress set up whenthe fuse has blown between conductingmembersconnected to the two ends of thefuse, and means whereby the fusecan beV withdrawn through the upper end of the insulating tube forisolating purposes.` i

10'.. A potential transformer fuse mounting for high voltage electricswitchgear, comprising a potential transformer tank, a condenserl typebushing insulator which supports the 4fuse mounting in the wall of thetank, a'metal tube constituting the innermost layer of the bushinginsulator, a potential transformer fuse disposed within Athe bushinginsulator,

an insulating tube surrounding the fuse and surrounded by the metaltube, a limiting resistance connected in series withthe fuse and mountedon the upper end thereof, and means y whereby the fuse can be withdrawntogether with the limiting resistance through the-upper end of the'insulating tube for isolating purposes.

11. A potential transformer-fuse mounting f for high voltage electricswitchgear, comprisl' ing a potential transformer tank, a condensertypebushing insulator in the wall thereof, a conductorwithin thebushinginsulator connected to the potential transformerv primarywinding, an insulating tube formed of layers of insulating material anddisposedA coa'Xially with ther bushing insulator, a potentialtransformer fuse mounted within such insulating tube with its lower endconnected :to theupper end of the conductor within the bushinginsulator, a rContact on the insulating tube constituting a terminal forconnection to' an external circuit, alimiting resistance mounted withits upper end connected to such contact and its lower end in`contactvwith the upper end of the fuse, means whereby the fuse can bewithdrawn together with the limiting resistance through the upper end ofthe insulating tube for isolating purposes, and overlapping conductinglayers of short length interleaved with the insulating layers of theinsulating tube and acting to grade the stress set up when the fuse hasblown between the lovgr end of the fuse and the contact on the tu 12.The combination with the features set forth in claim 1, of a chamberwhich is disposed above the potential transformer tank and through whichthe insulating tube passes, a contact on the insulating tube to whichthe upper end of the fuse is connected, a contact in the chamberconnected to an external electric circuit, a contact in the chamberconnect* ed to earth, and an isolating switch in the chamber which canbe moved to connect the contact on the insulating tube either to thecircuit contact or to the earthed contact.

13. The combination with the features set forth in claim 1. of acircuit-breaker tank di sposed by the side of the potential transformertank, a circuit-breaker immersed in oil therein, a chamber which isdisposed above the two tanks and through which the insulating tubepasses, a conductor leading from one of the contacts of thecircuit-breaker into the chamber, a contact in the chamber connected toan external circuit, an isolating switch controlling the connectionbetween such contact and the conductor leading to the circuitbreaker, acontact on the insulating tube to which the upper end of the fuse isconnected, and a second isolating switch in the chamber' controlling theconnection between such contact and the contact connected to theexternal circuit.

14. The combination with the features set forth in claim 5, of a chamberwhich is disposed above the potential transformer tank and through whichthe insulating tube passes, a contact in the chamber connected to theexternal electric circuit, a contact in the chamber connected to earth,and an isolating switch in the chamber which can be moved to connect thecontact on the second metal tube either to the circuit contact or to theearthed contact.

15. The combination with the features set forth in claim 8, of achamberwhich is disposed above the potential transformer tank and through whichthe insulating tube passes, a contact on the insulating tube to whichthe upper end of the fuse is connected, a contact in the chamberconnected to an external electric circuit, a contact in the chamberconnected to earth, and an isolating switch in the chamber which can bemoved to connect the contact on the insulating tube either to thecircuit contact or to the earthed contact.

16. The combination with the features set forth in claim 11, of achamber which is disposed above the potential transformer tank andthrough which the insulating tube passes, .a contact in' the chamberconnected to the external electric circuit, a contact in the chamberconnected to earth, and an isolating switchin the chamber which can bemoved to connect the contact on the second metal .tube either to thecircuit contact or to the earthed contact.

17. The combination with the features set forth in claim 3, of a chamberwhich is disposed above the potential transformer tank and through whichthe insulating Atube passes, a contact on the insulating tube to whichthe upper end of fuse is connected, a contact in the chamber connectedto an eX- ternal electric circuit, a contact in the chamber connected toearth, an isolating switch in the chamber which can be moved to connectthe contact on the insulating tube either to the circuit contact or tothe earthed contact, a cover for the upper end of the insulating tube,and means for preventing removal of the cover to permit the fuse to bewithdrawn unless the isolating switch is in its earthed position.

18. The combination with the features set forth in claim 8, of a chamberwhich is disposed above the potential transformer tank and through whichthe insulating tube passes, a contact on the insulating tube to whichthe upper end of the fuse is connected, a contact in the chamberconnected to an external electric circuit, a contact in the chamberconnected to earth, an isolating switch in the chamber which can bemoved to connect the contact on the insulating tube either to thecircuit contact or to the earthed contact, a cover for the upper end ofthe insulating tube, means whereby the fuse can be withdrawn through theupper end of the insulating tube when the cover is removed, and meansfor preventing removal of the cover unless the isolating switch is inits earthed position.

19. A potential transformer fuse mounting for high voltage electricswitchgear, comprising a potential transformer tank, a condenser-typebushing insulator in the wall thereof, a conductor within the bushinginsulator connected to the potential transformer primary winding, aninsulating tube formed of layers of insulating material and disposedcoaxially with the bushing insulator, a potential transformer fusemounted within such insulating tube with its lower end connected to theupper end of the conductor within the bushing insulator, overlappingconducting layers of short length interleaved with the insulating layersof the insulating tube and acting to grade the stress set up between thetwo ends of the fuse when the fuse has blown, a circuit-breaker tankdisposed by the side of the potential transformer tank, acircuit-breaker immersed in oil therein, a chamber which is disposedabove the two tanks and through which lthe insulating tube passes, a`conductor leading from one of the contacts of the '15 Circuit-breakerinto the chamber, a Contact in the chamber connected to an externaloircuit, an isolating switch eontrollingthe con-v nection between suchContact and the conductor leading to the circuit-breaker, a Con- 10 tacton the insulating tube to which the upper end of the fuse is Connected,and a second isolating switch in the chamber controlling the connectionbetween such Contact and the Contact connected to the external circuit.15 Invtestimony whereof we have signed oui` names to this specification.v

JOHN CHRISTIE. g DONALD FOSTER AMER.

